As this type of technique, there is conventionally known a cooling apparatus disclosed for example in Patent Document 1 listed below. This cooling apparatus includes an air supply system, a water supply system, a sprayer, and others. The sprayer is configured to mix water and compressed air and spray the water and air in a mist form to a workpiece. The heat of the workpiece is removed by a quantity of heat including latent heat generated when the mist impinges on an upper surface of the workpiece and then evaporates. The workpiece is cooled in this manner. At that time, the flow amount of water to be supplied to the sprayer is controlled so that the temperature to be detected by a temperature detecting device becomes a target temperature.